Build: cancel old builds

This commit implements a simple logic to cancel old running builds when a new
build for the same project/version arrives:

1. look for running builds for the same project/version
2. if there are any, it cancels them all one by one via Celery's revoke method
3. trigger a new build for the current commit received

Note that this new feature is behind a feature flag (`CANCEL_OLD_BUILDS`) for
now so we can start testing it on some projects that have shown their interest
on this feature.

The current behavior for `DEDUPLICATE_BUILDS` will be replaced by this new logic
in the future. However, it was not removed in this commit since it's still
useful for projects that won't be using the new feature flag yet.

Closes #8961

readthedocs/core/utils/__init__.py

@@ -124,56 +124,86 @@ def prepare_build(
         )
 
     skip_build = False
-    if commit:
-        skip_build = (
+    # Reduce overhead when doing multiple push on the same version.
+    if project.has_feature(Feature.CANCEL_OLD_BUILDS):
+        running_builds = (
             Build.objects
             .filter(
                 project=project,
                 version=version,
-                commit=commit,
             ).exclude(
                 state__in=BUILD_FINAL_STATES,
             ).exclude(
                 pk=build.pk,
-            ).exists()
+            )
         )
+        if running_builds.count() > 0:
+            log.warning(
+                "Canceling running builds automatically due a new one arrived.",
+                running_builds=running_builds.count(),
+            )
+
+        # If there are builds triggered/running for this particular project and version,
+        # we cancel all of them and trigger a new one for the latest commit received.
+        for running_build in running_builds:
+            cancel_build(running_build)
     else:
-        skip_build = Build.objects.filter(
-            project=project,
-            version=version,
-            state=BUILD_STATE_TRIGGERED,
-            # By filtering for builds triggered in the previous 5 minutes we
-            # avoid false positives for builds that failed for any reason and
-            # didn't update their state, ending up on blocked builds for that
-            # version (all the builds are marked as DUPLICATED in that case).
-            # Adding this date condition, we reduce the risk of hitting this
-            # problem to 5 minutes only.
-            date__gte=timezone.now() - datetime.timedelta(minutes=5),
-        ).count() > 1
-
-    if not project.has_feature(Feature.DEDUPLICATE_BUILDS):
-        log.debug(
-            'Skipping deduplication of builds. Feature not enabled.',
-            project_slug=project.slug,
-        )
-        skip_build = False
+        # NOTE: de-duplicate builds won't be required if we enable `CANCEL_OLD_BUILDS`,
+        # since canceling a build is more effective.
+        # However, we are keepting `DEDUPLICATE_BUILDS` code around while we test
+        # `CANCEL_OLD_BUILDS` with a few projects and we are happy with the results.
+        # After that, we can remove `DEDUPLICATE_BUILDS` code
+        # and make `CANCEL_OLD_BUILDS` the default behavior.
+        if commit:
+            skip_build = (
+                Build.objects.filter(
+                    project=project,
+                    version=version,
+                    commit=commit,
+                )
+                .exclude(
+                    state__in=BUILD_FINAL_STATES,
+                )
+                .exclude(
+                    pk=build.pk,
+                )
+                .exists()
+            )
+        else:
+            skip_build = (
+                Build.objects.filter(
+                    project=project,
+                    version=version,
+                    state=BUILD_STATE_TRIGGERED,
+                    # By filtering for builds triggered in the previous 5 minutes we
+                    # avoid false positives for builds that failed for any reason and
+                    # didn't update their state, ending up on blocked builds for that
+                    # version (all the builds are marked as DUPLICATED in that case).
+                    # Adding this date condition, we reduce the risk of hitting this
+                    # problem to 5 minutes only.
+                    date__gte=timezone.now() - datetime.timedelta(minutes=5),
+                ).count()
+                > 1
+            )
 
-    if skip_build:
-        # TODO: we could mark the old build as duplicated, however we reset our
-        # position in the queue and go back to the end of it --penalization
-        log.warning(
-            'Marking build to be skipped by builder.',
-            project_slug=project.slug,
-            version_slug=version.slug,
-            build_id=build.pk,
-            commit=commit,
-        )
-        build.error = DuplicatedBuildError.message
-        build.status = DuplicatedBuildError.status
-        build.exit_code = DuplicatedBuildError.exit_code
-        build.success = False
-        build.state = BUILD_STATE_CANCELLED
-        build.save()
+        if not project.has_feature(Feature.DEDUPLICATE_BUILDS):
+            log.debug(
+                "Skipping deduplication of builds. Feature not enabled.",
+            )
+            skip_build = False
+
+        if skip_build:
+            # TODO: we could mark the old build as duplicated, however we reset our
+            # position in the queue and go back to the end of it --penalization
+            log.warning(
+                "Marking build to be skipped by builder.",
+            )
+            build.error = DuplicatedBuildError.message
+            build.status = DuplicatedBuildError.status
+            build.exit_code = DuplicatedBuildError.exit_code
+            build.success = False
+            build.state = BUILD_STATE_CANCELLED
+            build.save()
 
     # Start the build in X minutes and mark it as limited
     if not skip_build and project.has_feature(Feature.LIMIT_CONCURRENT_BUILDS):

readthedocs/projects/models.py

@@ -1859,12 +1859,13 @@ def add_features(sender, **kwargs):
     DEFAULT_TO_FUZZY_SEARCH = 'default_to_fuzzy_search'
     INDEX_FROM_HTML_FILES = 'index_from_html_files'
 
-    LIST_PACKAGES_INSTALLED_ENV = 'list_packages_installed_env'
-    VCS_REMOTE_LISTING = 'vcs_remote_listing'
-    SPHINX_PARALLEL = 'sphinx_parallel'
-    USE_SPHINX_BUILDERS = 'use_sphinx_builders'
-    DEDUPLICATE_BUILDS = 'deduplicate_builds'
-    DONT_CREATE_INDEX = 'dont_create_index'
+    LIST_PACKAGES_INSTALLED_ENV = "list_packages_installed_env"
+    VCS_REMOTE_LISTING = "vcs_remote_listing"
+    SPHINX_PARALLEL = "sphinx_parallel"
+    USE_SPHINX_BUILDERS = "use_sphinx_builders"
+    DEDUPLICATE_BUILDS = "deduplicate_builds"
+    CANCEL_OLD_BUILDS = "cancel_old_builds"
+    DONT_CREATE_INDEX = "dont_create_index"
 
     FEATURES = (
         (ALLOW_DEPRECATED_WEBHOOKS, _('Allow deprecated webhook views')),
@@ -2015,6 +2016,12 @@ def add_features(sender, **kwargs):
             DEDUPLICATE_BUILDS,
             _('Mark duplicated builds as NOOP to be skipped by builders'),
         ),
+        (
+            CANCEL_OLD_BUILDS,
+            _(
+                "Cancel triggered/running builds when a new one for the same project/version arrives"
+            ),
+        ),
         (
             DONT_CREATE_INDEX,
             _('Do not create index.md or README.rst if the project does not have one.'),